Pues no le veo el problema... Este código funciona:
Código:
Option Explicit
Private Sub Command1_Click()
Open "C:\prueba.txt" For Append As 1
Write #1, Text1.Text
Write #1, Text2.Text
Close #1
End Sub
Private Sub Command2_Click()
Dim Uno As String
Dim Dos As String
Open "C:\prueba.txt" For Input As 1
Do While Not EOF(1)
Input #1, Uno
Input #1, Dos
If Dos = Text3.Text Then
MsgBox "Encontrado " & Dos
End If
Loop
Close #1
End Sub